FIG. 1 is a block diagram illustrating configuration of a radar receiver using a conventional deramping structure.
Referring to FIG. 1, a radar receiver using a conventional deramping structure includes a signal synthesizing unit 10, a receiving unit 20, and a compression and transmission unit 30. The receiving unit 20 includes an IF (Intermediate Frequency) filter, a synthesizer, a low pass filter (LPF), and an analog to digital converter (ADC), thereby converting a synthesized signal into a baseband received signal. The compression and transmission unit 30 includes a BAQC (Block Adaptive Quantization) unit, a formatter, and a downlink, thereby transforming the received signal according to a compression and storage format and downlinking the received signal to a ground station.
As shown in FIG. 1, noise tones such as a spurious tone or a harmonic tone added by an external clock or power do not appear in the time domain. However, in the deramping circuit, noise appears in the form of tone after passing through an IF filter and a matched filter.
FIG. 2 illustrates a spurious tone effect in the deramping operation. As shown in FIG. 2, the influence of the noise tone appears in the form of tone in the frequency domain, and finally appears as an undesired bright line in the actual image due to the nature of deramping, in which the frequency domain is a distance domain.
In the prior art, the aforementioned issue is addressed in hardware. However, after implementation of hardware, the issue may be raised again with aging or impact during operation. In addition, this issue is fatal in special cases, such as satellite systems, which cannot be accessed after launch.